I have a 1950s home and it started to smell like poop in the basement. It didn't overflow, I see the water, but when the cap is off the smell is terrible.
There's a hole in the concrete floor where the sewage/waste cleanout is and an old cast iron plug that's 1/4"-3/8" too big for the hole so it just sits on top (from whoever left it).
I've gone to big box stores and bought a 3 1/2" and 4" cleanout plug, and the same sizes for expandable test plugs.
The cast iron pipe area I cleaned out with a screw driver and a tooth brush, and I don't see any threads (large or small).
The 4" sizes are roughly 1/4" too big and the 3 1/2" would fall through.
Is there any other option just to plug it even if temporarily so I'm not breathing this in for days to come?
I used a plastic container to sit on top, weighted down, and I placed plywood on top of the hole to seal it temporarily but it is not effective.